CONDUCTIVITY AND HALL-EFFECT IN THE 2-DIMENSIONAL HUBBARD-MODEL

A path-integral field-theoretic derivation of electromagnetic linear response for the two-dimensional Hubbard model is given. We find, remarkably, that changes in the Fermi-surface topology associated with incommensurate planar spin-density-wave saddle points induce a change in sign of the Hall coefficient at dopings delta(H) = 0.02-0.5 for U/t = 2-10. The change in sign is not affected by short-range magnetic domains. We delineate from first principles an anomalous temperature dependence of the Hall carrier density at dopings close to delta(H). An additional anisotropic component to the usual dc conductivity is nonvanishing for certain types of spirals. The paper extends the Bloch-Boltzmann theory to the case of untraditional Fermi liquids where the damping of the quasiparticles is GAMMA(epsilon) approximately max(k(B)T, epsilon).